FYI: No need to edit /etc/default/grub as long as GrUB is working properly.

For either init or systemd Linux systems all* you have to do is:

* When the GrUB menu appears at boot, navigate to the Linux OS you want to modify and press e* Navigate down to the linux command line and place a 3 at the end of it* Press F10 to boot

It boots into command line interface(CLI) which is actually init level 3.Then do the nVidia install steps.

Note that " 3" works any time one needs to boot to 'text mode', i.e., the CLI(init 3). This is very handy for updating core parts of the OS, especially if SystemD is one of those parts, .

{ *all assumes a std GrUB install that is not hidden, write or password protected. If any of those are true then at least password is needed ... but for the people who use such a GrUB, this guide is prbly not needed anyway. }